1. Field of the Invention
This invention relates to a method of maintaining and cleaning brushes which remove semiconductor wafer cleaning compositions and, in particular, to a method of removing residual cleaning compositions from the brushes.
2. Description of Related Art
The presence of foreign material on semiconductor wafers presents a serious problem to the manufacture of integrated circuits on the wafers. In processing semiconductors, the wafers are normally initially polished to planarize the surface prior to subsequent processing to deposit the desired circuits. Chemical-mechanical polishing (CMP) is typically used and requires the introduction of a polishing slurry onto the surface of the semiconductor wafer as it is mechanically polished on a polishing table. The slurries typically are water based and may contain fine abrasive particles and incorporate chemical cleaning compositions, such as silica (SiO.sub.2), and alumina (Al.sub.2 O.sub.3). After polishing is complete, the wafers must be cleaned to completely remove residual slurry and other cleaning compositions in order that the surface be made ready for subsequent photolithographic processing and other manufacturing steps.
Brush cleaning utilizing cylindrical brushes have been typically used to clean residual cleaning compositions from the surfaces of semiconductor wafers. As these cleaning brushes remove the residual cleaning composition from the wafer surface, the residue builds up on the surface of and within the brushes themselves. These brushes may be made of a foam such as polyvinyl alcohol (PVA). In prior art systems, it has not been effective to clean such brushes and they typically have been discarded after an undesirable amount of residual cleaning composition has been built up on the brush. Because of cost pressures, these dirty brushes are sometimes utilized beyond the point where they should be replaced, which has resulted in inconsistent levels of cleanliness on the wafers from batch-to-batch and job-to-job, and has contributed to lowering yield of semiconductor product wafers.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved method of maintaining and cleaning brushes which remove semiconductor wafer cleaning compositions whereby residual cleaning compositions are efficiently and thoroughly removed from the brushes.
It is another object of the present invention to provide a method of maintaining and cleaning brushes which permits the brushes to be reused after they would normally be discarded due to buildup of residual cleaning composition.
A further object of the invention is to provide a method of reducing the cost of maintaining semiconductor wafer cleaning brushes.
It is yet another object of the present invention to provide a method of maintaining and cleaning semiconductor wafer cleaning brushes which attains more consistent cleaning of wafers from batch to batch.
It is a further object of the present invention to provide a method of extending the lifetime of semiconductor wafer cleaning brushes.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.